Clinical evaluation of a new alkylating agent: Cytoxan (cyclophosphamide)

A B As found in earlier work,4 the attachment of a phosphoryl group (B) to nitrogen mustard (A) reduces the chemical activity of the parent compound by diminishing the basic properties of the central nitrogen atom and thus in turn decreasing the ionizability of the chlorine atoms in the chloroethyl groups. For the activation of cyclophosphamide, phosphamidases or phosphatases are theoretically needed to break the cycle group at the phosphorous-nitrogen or the phosphorous-oxygen bonding respectively: thus, the compound is relatively inert until i t is incorporated into cells containing these enzymes. By histochemi-